Moustapha Sarr, a senior official with PUR, said 20 of the arrests were supporters of Issa Sall.

Macky Sall and Issa Sall share the same surname but are not related.

Tambacounda public prosecutor Demba Traore said the arrests were mainly members of Issa Sall’s security guard, and police had seized knives and clubs on PUR members.

Eight journalists who were covering Issa Sall’s campaign were hurt when their minibus was attacked by suspected supporters of the ruling coalition, organisations representing media workers said.

Senegal, a former French colony, has been buffeted by violence ahead of the February 24 vote, which Macky Sall hopes to win outright in the first round.

On Sunday at least two people were “seriously injured” in Fatick, a presidential stronghold in Senegal’s centre-west, in clashes with supporters of rising opposition candidate Ousmane Sonko, local media reported.

Four people, all Sonko supporters, were badly hurt on February 4 in the northern city of Saint-Louis, Sonko’s campaign said.

Issa Sall said on Twitter on Tuesday that after the “tragic events” in Tambacounda, he would be “suspending” his campaign and heading back to the capital.

On Monday, the president called for calm but took aim at his predecessor and political rival, Abdoulaye Wade, who last week called for his supporters to burn their electoral registration cards and ballot sheets.

The clashes “are the result of the call for violence by certain political leaders… who will be brought before the courts to account for their acts,” President Sall said.

Senegal’s election campaigns are often marred by accusations of corruption, influence-peddling and dirty tricks, misinformation, although the country is also often held up as a beacon of democracy and relative prosperity in West Africa.